The growth of plants usually are influenced by many environmental factors, wherein drought and/or salt damage are main factors resulting in great reduction of crop production in many areas. Thus, it always a major aim to develop crop species with stress tolerance in researches of agricultural science and technology.
For resisting or adapting to disadvantageous environmental factors, plants receive extracellular changes of environmental conditions and transfer them through many pathways into cells to induce expressions of some responding genes and generate some functional proteins, osmoregulation substances as well as transcription factors for signal transmission and gene expression regulation so that plants are able to make corresponding responses to environmental changes and avoid damages caused by drought, high salt and/or low temperature stresses. (Xiong et al, Cell signaling during cold, drought and salt stress. Plant Cell. 14 (suppl), S165-S183, 2002). The regulating factors finely regulate the expression of functional genes for responding environmental changes. When plants encounter stresses, transcription factor as a controlling gene is able to regulate the expression of a series of downstream genes to enhance the tolerance of plants to the stresses.
Kawasaki et al (2001) utilized microarrays to analyze the early expression profile of rice under high salt stress, and disclosed that a great number of genes were induced or inhibited and the induction and expression of these genes were regulated by transcription factor (Kawasaki S, Borchert C, Deyholos M, Wang H, Brazille S, Kawai K, Galbraith D and Bohnert H J. Gene expression profiles during the initial phase of salt stress in rice, Plant Cell, 2001, 13: 889-905). It is found that transcription factor families of AP2/EREBP, Zinc finger, Myb, bZIP in Arabidopsis thaliana are induced to be expressed or inhibited under different stresses (Shinozaki K et al, Monitoring the Expression Pattern of 1300 Arabidopsis Genes under Drought and Cold Stresses by Using a Full-Length cDNA Microarray, Plant Cell, 2001, 13: 61-72). Thus, it is deemed that these transcription families are very important in regulation during the procedure of plant response to stresses. Therefore, the separation and identification of transcription factors having core regulation function for response to stresses and the use thereof for genetic improvement of crop to resist stresses are important and meaningful for seed breeding.
Based on the known information of Arabidopsis thaliana transcription factors, some studies have been done to improve plant tolerances. Transgenic Arabidopsis thaliana plants cultured by using EREB1A and DREB2A have higher tolerances to low temperature, drought and high salinity than the wild type (Liu Q et al, Two transcription factors, DREB1 and DREB2, with an EREBP/AP2 DNA domains separate two cellular signal transduction pathways in drought—and low-temperature-responsive gene expression, respectively, in Arabidopsis. Plant Cell. 1998, 10: 1391-1406). The research group of Thomashow M F in Michigan State University (U.S.A.) also cultured plants with enhanced freezing tolerance by using Arabidopsis thaliana CBF1 gene in genetic transformation.
Rice is one of the most important alimentary corps. The tolerance to drought and/or salt is particularly important for rice. However, no transgenic rice plant with tolerance to drought and/or salt has been developed so far. Thus, it is meaningful and important to find out transcription factor associated with tolerance to drought and/or salt for culturing a rice plant with tolerance to drought and/or freezing and thereby increasing rich production.